Power tube structure



Api'il 18, 1944. c, y. 0 2,346,929

l owm TUBE STRUCTURE Filed June 6, 1942 2- Sheets-Sheet l INVENTOR CHARLES l. LITTa/v ATTORNEY April 18; 1944. c. v LlTTON 2,346,929

POWER TUBE STRUCTURE Filed June 6, 1942 2 Sheets-Sheet 2 .er 5.. 45 I I F 5' U Wu/4e INVENTQTT CHARLES 1 arm/v Patented Apr. 18, 1944 POWER TUBE STRUCTURE Charles V. Litton, Redwood City, Calif., assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application June 6, 1942, Serial No. 446,034

7 Claims. (Cl. 250-275) This invention, relates to vacuum tubes and more particularly to high power vacuum tubes such as are used in radio transmitters.

Vacuum tubes have been constructed in small sizes in which the filaments have a very high electron emission and the anodes are so constructed as to dissipate the heat generated b the electron stream and thus to have a larger power capacity than would otherwise be achieved. The technique of these smaller vacuum tubes, however, is not generally applicable for use in the large high power vacuum tubes.

It is the principal object of m invention to produce a high power vacuum tube having a large electron emission and an anode capable of dissipating the heat generated by the resulting electron high current without requiring that the vacuum tubes be of the large dimensions previously necessary for such power tubes.

According to one feature of my invention 1 provide a high emissive filamentary cathode divided into sections so that excessive filament sag will not occur and envelop this cathode structure by an'anode provided with liquid cooling means and so constructed that a relatively large temperature gradient between the internal surface of the'anodean the cooling medium is achieved.

A better understanding of my invention and the objects and features thereof may be had from a reading of the particular description of my inventlon made with reference to the accompanying' drawings in which Fig. 1 is a view or a vacuum tube in accordance with my invention partly in'section to show the construction; v

Fig. 2 is an alternative anode arrangement for use in a tube such as shown in Fig. 1; I

Fi 3 is a diagram explaining the operation of a metallic body in dissipating heat;

Fig. 4 is a view illustratin the structure of the cathode in accordance with m invention; and

Figs. 5 and 6 are simplified illustrations showing the electrical relationship of filaments in a cathode structure such as shown in Fig. 4.

Turning first to Fig. 1, I indicates a filamentary cathode of high electron emission. This cathode is preferably made of thoriated tungsten and is wound quadrifilar so that alternate wind- 'ings of the spiral carry current flowing in opposite directions. A more particularly description "of the cathode construction will be given later in connection with Figs. 4, and 6. v

Numeral H designates a grid of any desired known structure arrangedaround cathode I 0.

Arranged about cathode lo and grid H, and substantially enveloping it, is the anode of the tube comprising a metallic shell portion 12 on which are provided raised portions or' projections l3. Contacting these raised-portions I3 is wound a spiral coil l4 made up of hollow tubular member l5. Certain parts of this tube are in direct conductive connection with the projecting portion 13 of shell [2, and the otherportions are in direct conductive connection with the other turns of the tube or pipe l5. Thus, a continuous metallic conductive path from the inner surface of shell l2 to the outer atmosphere is provided. In tubular members I5 is circulated a cooling liquid, preferably water. I m

The particular structure illustrated in Fig. 1 enables a great amount of heat to be dissipated from the internal surface of anode shell I2 so that the tubes may operate at a much higher concentration of energy than a conventionally built tube of the same size. The reason for this may be better understood by a brief reference to Fig. 3 in which a metallic member an is shown. This member 30 has applied to it heat on the under surface, points 3| and 35 of which may be'considered as representing unit areas or specific points of a continuously heated sheet. A the heat from point 3| travels outwardly through the metal, it tends to spread along the metal as indicated by lines 32 and 33. It is, therefore, clear that if the metal is made thicker as it is at point 35, a greater spread will occur, as shown at 36, 31. Where the metal is relatively thin, as at point 3|, a tremendous temperature gradient must be maintained between the heating point 3| and the outer surface of the metal if a large amount of cooling is desired. If water cooling is used this means that a huge volume of water must be circulated over the surface in order to dissipate the heat, since the heat transfer can take place over only a relatively narrow surface or water. Thus, if water cooling is provided, a large circulation of water must be provided in order that sufficient water contacts point ill to maintain the proper cooling. The volume of water which can be circulated effectively is also limited since at the higher velocities thewater will not as thoroughly wet the surface and thereforewill not provide for efiicient heat transfer. I I Q By use of a thicker section of metal as indicated at point 35, the area over which heat transfer to the water may take, place is. greatl increased. Likewise, because of the addedthickness of metal a smaller temperature gradient need exist within w nfii fi 1'- am? .4 2. are "c nnected together at their [fonds adjacent d'i'sc f4? anda're" connected to feeding "conductor Lil fivound units. If desired the windings may be plished as shown in Fig. 1 by having the metallic pipe in which the circulating water is carried in direct conductive connection theinner shell I2 of the anode. Thus, the teih ip erature gra'di ent from the center of the 1511811" 130:13'1'16 cooling 7 water so that a large cooling surface is presented.

it can be seen that ii projections are provided as ho F g.1; t e p t fe i eds ie 'if el fi i e the n rte-peer th' shell butup tlflbllgh euee pr ee iene B a d the walls r tube 1-5; Accordingly, an extremely efficie'ntheat treesfer "is ac o ishment: the anode may mereq i hetd e a diet mu'e h h t m cen 'jfi hasmei s w e.st q fi v P- era'te'd :to regaeejmg er output currents sin'ce h ikie t n'e' th anod Usuall is h l tin'g factor in the power handling capacity of i i b I v nne- 2' al ma iv s ietsre he d infFig, l forthejandde fshown. *In thisr'arrar'igeme'n't the "shell I 2 is not providedwith prejections, Tube members 25 are provided-andare directly in lc'ontact with the oute r suria ce of shell I 2. H shdwnjnlth is figure the tubes are made square in forrn sothat -a flarger "surface thereof will be in'contact wi-th the outer wall oi shell [2. this arrangement a continuous conductivef hat path is provided mm the inner wan 'of fsn il :12 through tl'rfe fival ls of tube 25, and th'usan eiii 'clent heat transfer to the cooling jindium circulating in the tube 25 is pro:

examples which fmay be constructed "within The a h n b i r ie s n "In Fig. is shownfafstructural f'a rangerjnent 'of a erearen ry eathodeflfl made to produce l i li r i f mis de ting jcathode' is" "current"s'upply lines 44, its fexten'd "through in- 14. Similarly, *windi'rigs'if eridi q are'eo'ri neeted together at their ends andffas'tenedto feeder "end an or "conductors 4e,

liarlyf the, other I windings comprising four together to conductor 44, while 52 and 54 are connected together to conductor 45.

A better showing of the interconnection of the windings of Fig. 4 may be had by reference to the simplified circuit arrangement shown in Fig. 5.

It is clear that while the structural arrangement of Fig. 4 has been illustrated 'thefilamentary cathode in accordance with my invention need not be limited to two such quadrifilar multiplied ii-1 number. For example, in Fig. 6 there are shown four units connected together as in Fig. 5. The first two unit arrangements may be identical to those shown in Fig. 5 and accordingly the same reference characters have been applied thereto. Conductors 44, 45, however, continue upwardly beyond a further disc 65. Further still is provided another disc 66. Two additional sets of windings 56, 51, 58, 59 and 61, 5 2, G3 and '64, corresponding to 46 to 48 and 5| to 54, inclusive, are arranged 'endito end with the other pair "of wihdings- These windings are connected together similarly to conductors '44 and 45 "so that. the entire's'ystem is fed in parallel. It should be understood that the separate units "eachcomprise four spiral woundconductors a'sshown in Fig.4.

It is further clear that this "extension-maybe continued to include as many cathode units as is desired. For example, it it is not desired to use four but to use three *units this may be -accomplished merely by omitting the top set of windings Bl to 64, and terminating the cathode at disc 65. Furthermore, iffitrisj-desired,sepa- -rat'e pairs of lead-in "conductors, may .be con- 'nected in parallel at th "lower end and brought into the junction point between any two units instead of using the single conductor .;pair as shown'inthesimplified-iormofFig.5. I

By using short units of the form illustrated-in the drawing, -the=fiiaments may be-heatedtma high temperature but because of the shortness of the spirals will-not -sag and cause distortion and possible'short circuits inthe itube. B y the use of this arrangement the entire-filament structure may be -made as long as desired without weakening the cathode as 'a whole and without increasing the dangerof short circuiting or sagl While -I have specifically {desribed ipartioular examples of my invention it should be 'iinde'rstood that manychanges may ibe made'withih the scope -o f invention wirheue uepartmg from the spirit thereof. l

It should also be appreciated thattlie features of my invention ma be applied to'var'ioiis types of vacuum tubs diife'ring considerably in coning in each'un itthe"'w'iridifigs"in'sris parallel connection so that currntilows in eppqsite directioris in "adjacent 'of s'aid "spifalsftlrie series connected enaser nae 'dingsluem eenother, and means for mechanically supporting said units, said anode comprising a metallic shell surrounding said cathode and grid and means for developing a relatively low temperature gradient within the metal between the internal surface of said shell and a cooling medium including liquid carrying metallic pipes wound about said shell and in direct thermal contact therewith.

2. A high power vacuum tube according to claim 1, wherein said anode metal shell is provided with externally projecting portions to further extend the metallic thermal path to further lower the temperature gradient, said metallic tubing being in conductive contacting relation with said projections.

3. A vacuum tube cathode comprising a plurality of spiral quadrifilar wound filamentary cathode units positioned end to end, means for connecting in each unit the windings in series parallel connection so that current flows in 0pposite directions in adjacent turns of said spirals, the series connected ends of the windings being connected to a common point, means for feeding said units in parallel with respect to one another, and means for mechanically supporting said units.

4. A vacuum tube filamentary cathode comprising a pair of feeding conductors, a central supporting rod, discs fixed to said rod at predetermined spaced intervals, at least two filamentary units positioned end to end, each comprising four spiral conductors forming a quadrifilar filament winding, one end of said spirals all being connected together at one of said discs, the other ends of said spirals being connected in pairs to respective ones of said feeding conductors.

5. A vacuum tube filamentary cathode comprising a pair of feeding conductors, discs fixed at predetermined spaced intervals, at least two filamentary units positioned end to end, each comprising four spiral conductors forming a quadrifilar filament winding, one end of said spirals all being connected together at one of said discs, the other ends of said spirals being connected in pairs to respective ones of said feeding conductors.

6. A vacuum tube according to claim 5, wherein four end to end filamentary units are provided, the adjacent ends of the two centrally positioned units being connected to a common disc, further comprising heat shield discs insulated from said filamentary units arranged between units at the ends connected to said feeding conductors.

7. An anode for a vacuum tube having a cathode and a control grid surrounding the cathode said anode comprising a metallic shell surrounding said cathode and grid means for developing a relatively low temperature gradient within the metal between the internal and external surfaces of said shell, including raised portions formed on said metallic shell on the external surface thereof, and a cooling means including liquid carrying metallic pipes wound about said shell and in direct thermal contact with the raised portions on said shell.

CHARLES V. LITTON. 

